Download Interesting Case Series Review of Facial Nerve Anatomy

Interesting Case Series
Review of Facial Nerve Anatomy: Trauma to the
Temporal Region
Will Schleicher, MD, Michael Feldman, MD, and Jennifer Rhodes, MD
Department of Surgery, Division of Plastic Surgery, Virginia Commonwealth University,
Richmond
Correspondence: [email protected]
Keywords: facial nerve, SMAS, temporoparietal fascia, stylomastoid foramen, temporal branch
DESCRIPTION
A 25-year-old man presented as a trauma alert to the emergency department after being
involved in a motor vehicle crash. After appropriate ATLS (advanced trauma life support)
evaluation, a large bulky head wrap was removed revealing a 25-cm transverse laceration
extending from the medial brow traversing the most cephalad portion of the right superior
helix, and extending toward occiput.
QUESTIONS
1. What is the course of the main trunk of the facial nerve after it exits the
cranium?
2. Where does the facial nerve divide?
3. What are the branches of the facial nerve?
4. Through which tissue planes does the facial nerve travel as it crosses the
temporal region?
DISCUSSION
The patient presented with a 20-cm, irregular, transverse, laceration with significant debris
in the wound base. This complex laceration to the right frontal/temporal region provides
an excellent opportunity to review the anatomy of the facial nerve. It is not uncommon
to encounter an unrestrained occupant of motor vehicle in the trauma setting. Without
restraining devices, patients regularly sustain polytrauma including facial fractures and
concomitant soft tissue injuries. As plastic surgeons treating these injury patterns, it is
vital to understand the anatomic foundations of the face. The basics of bony architecture,
vascularity, and innervation are among those necessary concepts to master.
A review of the anatomy in the temporal region is a point to return to in many traumatic
and elective surgical interventions due to the complexity of the facial planes enveloping the
facial nerve. The facial nerve exits the cranium at the stylomastoid foramen just inferior
and posterior to the auricle. It has the longest path within a bony canal of any nerve in
the body. Upon its exit of the cranium, the nerve courses within the parotid gland in a
superior medial direction. It is within the gland itself, at the pes anserinus, that it separates
into the temporozygomatic and cervicofacial divisions. These divisions course superior and
inferior, respectively. As the divisions proceed in an anterior direction, they separate into
5 branches: frontal/temporal, zygomatic, buccal, mandibular, and cervical. The temporal
region itself presents some of the most challenging anatomic layout due to the numerous
facial layers. The course of the temporofrontal branch can be estimated using external
landmarks as described by Pitanguy et al. A line starting from a point 0.5 cm below the
tragus in the direction of the eyebrow, passing 1.5 cm above the lateral extremity of the
eyebrow estimates the path of the nerve in the soft tissue.2
The temporal region is unique in its multitude of facial and muscular planes. The
nomenclature and unique extension of these planes contribute to the difficult understanding
of the anatomy of the region.
An understanding of these relationships is crucial to knowing the path of the facial
nerve. The 3 layers of fascia
in the temporal region which
have a close relationship to
the facial nerve are as follows: the temporoparietal fascia (also called the superficial temporal fascia) and the
deep temporal fascia (which is
composed of a superficial and
deep layer). The temporoparietal fascia is in direct continuity with the galea cephalad, the
Figure 1. Diagram of the spatial relationship of the facial
SMAS (superficial musculonerve in the temporal region coursing deep to the SMAS and
aponeurotic system) inferiorly,
superficial to the superficial layer of the deep temporal fascia.
the frontalis anteriorly, and the
Copyright by AO Foundation, Switzerland. Source: AO
Surgery Reference, www.aosurgery.org.
occipitalis posteriorly.
The temporal branch of the facial nerve courses within these planes at known levels
providing a road map for safe dissection.4 A review of this anatomy is beneficial to ensure
the safe dissection of tissue and avoidance of injury, as well as to establish an idea of injury
patterns.
Figure 2. Intraoperative
photograph post washout and laceration
repair.
Figure 3. Postoperative photographs at follow-up (a) 2 weeks, (b) 6 weeks.
REFERENCES
1. Norris CW, Proud GO. Spontaneous return of facial motion following seventh cranial nerve resection.
Laryngoscope. 1981;91:211-5.
2. Pitanguy I, Ramos AS. The frontal branch of the facial nerve: the importance of its variations in face
lifting. Plast Reconstr Surg. 1966;38:352-6.
3. Reitzen SD, Babb JS, Lalwani AK. Significance and reliability of the House-Brackmann grading system
for regional facial nerve function. Otolaryngol Head Neck Surg. 2009;140(2):154-8.
4. Stuzin JM, Wagstrom L, Kawamoto HK, Wolfe SA. Anatomy of the frontal branch of the facial nerve:
the significance of the temporal fat pad. Plast Reconstr Surg. 1989;83:265-71.
5. Seckel BR. Facial Danger Zones: Avoiding Nerve Injury in Facial Plastic Surgery. St Louis, MO: Quality
Medical Publishers; 1993.
Schleicher et al. Review of Facial Nerve Anatomy: Trauma to the Temporal Region. www.ePlasty.com, Interesting Case,
July 29, 2013